'This visit signals that the United States intends to remain engaged in Southeast Asia.'

The presence of a U.S. aircraft carrier in Da Nang, the first since the end of the Vietnam War, is serving as a signal from the Trump administration that it wants to enhance cooperation with Vietnam and its committment in the region, analysts said.

The USS Carl Vinson and two U.S. naval combat ships, carrying 6,500 crew members, arrived in Da Nang in central Vietnam for a five-day visit on Monday, a diplomatic milestone that has attracted global attention.

Professor Carlyle Thayer from the University of New South Wales at the Australian Defense Force Academy, said the USS Carl Vinson is sending a message that the U.S. will maintain its naval presence in the South China Sea and that Vietnam supports the presence of the U.S. Navy for regional peace and stability. The waters are known as the East Sea in Vietnam.

"Vietnam has been reassured by the Trump administration that it will enhance their comprehensive partnership," he said. "This visit signals that the United States intends to remain engaged in Southeast Asia."

The U.S. Navy visit arrives shortly after U.S. Defence Secretary James Mattis touched down in Hanoi in January, marking significant improvements in bilateral military relationships, experts said.

Murray Hiebert, a senior associate of the Southeast Asia Program at the Center for Strategic and International Studies (CSIS) in Washington, said that "The U.S. is sending a message that Vietnam is an important partner to the U.S. in Asia.

"Vietnam is sending a message that it sees the U.S. as an important hedge in the South China Sea."

The U.S. visit has won global media coverage by marking an historic development in the relationship between two former enemies.

Experts said the improvement comes at a time when both countries need partners to gain stronger footholds in the complicated region.

John Blaxland, director of the Southeast Asia Institute at the Australia National University, said the United States and Vietnam have transformed from "bitter enemies to surprisingly close strategic partners", and see each other as forthright defenders of one another in the neighborhood.

Derek Grossman, a senior defense analyst from the American global policy think tank RAND, said that by sending the Carl Vinson to Vietnam, the Trump administration is signaling that it wants to continue to uphold freedom of navigation in the South China Sea.

For Hanoi, by welcoming the most recognizable symbol of U.S. power to its shores, Vietnam is sending a clear message that it plans to leverage relationships with external powers.

"The Trump administration has been very clear about the need for Vietnam and the U.S. to work together in the South China Sea", said Grossman.

Defense relations between Vietnam and the U.S. have been strengthened since 2016, when President Obama decided to fully lift the ban on the sale of assault weapons to Vietnam. The Trump administration has also identified Vietnam as a “cooperative maritime partner”.

Thayer said that U.S.-Vietnam defense relations are poised to enter a new phase. Vietnam has spent $79 million on weapon purchases from the U.S. and that is likely to increase this year.

Dr. Le Hong Hiep, a political analyst from the Yusof Ishak Institute in Singapore, said the visit of Carl Vinson shows that the two countries are now much more comfortable than many years ago in conducting high-profile defense cooperation activities.

"This is a natural yet hard-earned outcome resulting from their continuous efforts to cultivate defense ties over the past 10 years," Hiep said.

He said the two countries might pick up that momentum to carry out more regular visits, amid challenges arising from the region’s geostrategic landscape.

"They should not be worried that such activities would “offend” a third party as long as they do not constitute a direct threat to that party," he said.